Air Canada and Virgin America offer the healthiest in-flight food, the latest annual survey of the fare available to passengers on flights.

The survey of 10 North American airlines' menus in December reveals an overall small increase in healthy and low-calorie food choices compared to the year before, says Charles Stuart Platkin, an assistant professor at CUNY School of Public Health at Hunter College in New York.

Platkin has assessed the nutritional value of airline food in six annual surveys. And too many unhealthy items continue to dominate many airline menus, he says.

"Airlines are still in the early stages of healthy offerings -- testing, learning and retesting," says Platkin, who edits the website DietDetective.com. "I believe, in years to come, airlines will realize that healthy and low-calorie offerings are what consumers are interested in purchasing and consuming."

Most in-flight food items have nutritional information on the packaging, but Air Canada stands out among airlines because it carries nutritional data sheets for passengers for all items it serves, Platkin says.

Using a zero-to-five-star scale, Platkin offers the following health scores for, and comments about, airlines' food. Scores are based on six criteria: number of healthy foods; calories; improvement from last year; menu innovation; variety, and cooperation in providing nutritional information.

Air Canada

Health score: ****

Comments: This airline cares about the health of its passengers. The food is called Air Canada NutriCuisine because of its freshness and quality of ingredients. Air Canada contracts with a company called Food With a Conscience to create its menus. The best snack is Nissin Foods' chicken ramen noodle soup. The meals are relatively low in calories. Go for the chicken or roast beef wrap or the vegetarian sandwich. The berry and vanilla oatmeal is also a great offering.

Virgin America

Health score: ****

Comments: The food has fewer calories and higher nutrient density than last year. It's great that Virgin America offers on-demand in-flight food ordering via a touch-screen on every seatback. You can order any time, not just when the carts come through. For snacks, the PopChips are a low-calorie choice, but the best choice is the mixed nuts. The oatmeal is a good breakfast choice, and the snack boxes, such as the protein meal with hummus, nuts and tuna, are great.

United Airlines, Continental Airlines

Health score: *** ¼

Comments: Continental and United have merged and, except for one item, they now offer the same food. Several years ago, United featured an amazing assortment of healthy offerings and was really focused on health. Now, there are only a few healthy choices, but most of the choices available for lunch and dinner have a reasonable calorie count. All the individual snacks are poor choices except for the roasted almonds, but they're high in calories and need to be shared with someone else. On flights longer than two hours, go for the tapas.

US Airways

Health score: ** ¾

Comments: The CaféPlus snack box is not a bad choice, because you get protein from the tuna, and it's low in calories. Maybe you can pass up the cookies that come with it. I also like the Cobb salad, and the good news is that the dressing is typically offered on the side. The only low-calorie individual snack is chips and salsa. Avoid the new bacon/egg salad croissant box at more than 700 calories.

JetBlue Airways

Health score: **¾

Comments: Last year, JetBlue started to offer more than just snacks but only on longer flights. The problem is they need to add some healthier meals and snacks. The individually packaged snacks are portion-controlled, but most lack nutritional value. The airline no longer offers nuts, which were the most nutrient-dense offering. For a free snack, opt for the Quaker Multigrain Fiber Crisps. For meal boxes, which can be purchased, the Shape Up is the clear winner. It has eight grams of fiber and only two grams of saturated fat.

American Airlines

Health score: ** ½

Comments: The snacks are high in calories with few healthy offerings. Your best bet is an individual snack, the Sabra roasted red pepper hummus with pretzels. If you're on a long flight, the best choice is a new item — Marcus Samuelsson's New American Table turkey and chutney sandwich. It's packed with protein and has apple slices.

Delta Air Lines

Health score: ** ¼

Comments: Individual snack choices are not very good, but meal choices on longer flights are reasonably healthy. Share the Flight Delights snack box unless it's your full meal. It has a variety of nutrient-dense foods that are low in calories. Of the breakfast options on long flights, your best bet is the breakfast snack, which has light yogurt and a banana. For lunch/dinner, the chicken and turkey Cuban is the lower-calorie choice, but try to eat only half the bread.

Southwest Airlines

Health score: * ¾

Comments: There's not much variety or nutritional value in the food offerings. Go for the nuts, and skip the pretzels and other items.

Spirit Airlines

Health score: *

Comments: Spirit's media department did not return repeated phone calls and e-mails for nutritional information. The information is on the food packaging, so check before you buy. The cup of noodles is only 300 calories and might suffice as a meal. Bring your own food.